Generally, to insert any catheter into a blood vessel, the vessel is identified by aspiration with a long hollow needle in accordance with the well known Seldinger technique. In its simplest application, a needle, with a syringe attached, is introduced into the patient. When blood enters the syringe, it provides visual indication that the vessel has been found; the syringe is then disconnected from the needle and a thin guidewire is then introduced into the needle and into the interior of the vessel. Commonly, upon disconnection of the syringe from the needle, bleeding can occur from the needle and onto the operative field, or air can be aspirated into the vessel if the patient inspires while the needle is not sealed prior to and during introduction of the guidewire into the needle. Blood on the operative field exposes the caregivers to contamination with blood-borne pathogens, and intravascular air can result in vascular occlusion and injury or death. The introducer needle is then removed from the patient and slid over the guidewire proximal end, leaving the distal end portion of the guidewire that has been inserted into the vessel within the vessel and the opposing end of the guidewire projecting beyond the surface of the skin of the patient.
At this point, several options are available to a physician for catheter placement. The simplest is to pass a catheter into the vessel directly over the guidewire. The guidewire is then removed, leaving the catheter in position within the vessel. However, this technique is only possible in cases where the catheter is of relatively small diameter, made of a stiff material, and not significantly larger than the guidewire. For example, this technique may be used to insert small single-lumen or dual-lumen catheters into a patient. If the catheter being inserted is significantly larger than the guidewire, a dilator catheter made of stiff material is passed over the guidewire to enlarge the hole. The dilator catheter is then removed, and the catheter is then passed over the guidewire into the vessel after which the guidewire is then removed.
One type of syringe and needle for use in introducing a guidewire into the vasculature is disclosed in U.S. Pat. No. 5,045,065. The syringe assembly includes a syringe barrel to which a distally projecting needle can be attached. The barrel contains a fluid chamber, and a tube attached to the distal base of the barrel projects proximally into the chamber and includes a proximal side hole within the barrel. A two-part plunger is slidable within and along the chamber and contains a centrally located guidewire passage therethrough; the proximal end of the tube also extends into the plunger's guidewire passage. A valve assembly is contained within the plunger near its proximal end and includes a pair of axially staggered valves within the plunger and traversing the guidewire passage to prevent fluid flow therethrough from the needle, or air passing therethrough from the open plunger proximal end, while permitting insertion therethrough of the guidewire.
In use, regarding the device of U.S. Pat. No. 5,045,065, the vessel is identified by first inserting the distal tip of the needle below the skin. The plunger is then withdrawn proximally to develop negative pressure within the barrel of the syringe. Traction on the plunger is then maintained while the syringe is advanced into the vessel. Upon the needle's distal tip entering the blood vessel, blood is aspirated into the syringe barrel through the side hole of the tube within the barrel's chamber. Once the vessel is identified, the plunger is advanced and aspirated blood is flushed back into the vessel. The guidewire is then inserted through the plunger and the valve assembly, through the guidewire passage tube in the barrel, through the needle and into the vessel of the patient.
Although the device of U.S. Pat. No. 5,045,065 represents a significant improvement over the standard syringe/needle technique as taught by Seldinger, its use has several drawbacks: (1) the plunger must be retracted as the syringe is advanced in the opposite direction; (2) the syringe is heavy and once the needle is in the vessel it must be supported by one hand of the practitioner, allowing only one hand for preparation and introduction of the guidewire; (3) even with the plunger seated within the barrel of the syringe, the distance from the guidewire entry into the plunger to the vessel is relatively long, and any inadvertent movement of the syringe during the procedure can dislodge the needle from the vessel; and, (4) negative pressure created by the practitioner as the syringe is advanced is operator-dependent and even though non-coring needles are used, if the negative pressure is too high, subcutaneous fat can be pulled into the needle causing occlusion and preventing blood entry into the barrel even when the needle enters the vessel.
In U.S. Pat. No. 6,277,100 is disclosed an introducer device that includes an integral aspiration bulb and no plunger, which disclosure is incorporated hereinto by reference. Such a closed system vascular guidewire introducer device is illustrated in FIGS. 1 and 2 hereof. The device includes a transparent flexible valved bulb to which a needle is removably attached at its distal end. A conduit extends from the proximal device end and through the bulb, and is aligned with the needle's channel, thus defining a passageway extending through the device for eventual insertion of a guidewire therethrough into the vasculature. The conduit includes a proximal valve traversing the conduit at the proximal end of the bulb, the valve being openable by the guidewire being inserted therethrough but otherwise remaining closed to seal the conduit. The device is operated by first compressing the bulb. The needle is then inserted under the skin and the pressure on the flexible bulb is released creating constant negative pressure on the needle. The device is then advanced into the blood vessel, and once the needle tip enters the blood vessel, blood is aspirated into the bulb by the negative pressure created on the flexible bulb. A guidewire is then introduced and passed through the valve contained within the bulb assembly and advanced into the vessel. The bulb and needle are then removed leaving the guidewire within the vessel. The advantages of this device are as follows: (1) the negative pressure necessary for aspiration of blood is not operator dependent but rather is maintained by the bulb once it is compressed and released; (2) the device is lightweight and in most adults does not require the practitioner to support it once the vessel is identified; and, (3) the length of the device is shorter than the syringe/needle combination described in the previous patent. Therefore, with these advantages, there is less likelihood of losing cannulation during the procedure.
Guidewires usually are tightly coiled wires that are known for their flexibility, and they range in size from about 0.018 in (0.457 mm) to 0.045 in (1.143 mm), with the smaller size guidewires being more flexible than the larger sizes. While the valve of the above-referenced bulb introducer permits passage of guidewires of most sizes, the valve has proven to be relatively stiff, and too often resists the insertion therethrough of guidewires of very small size, such as 0.018 in, which are known to be highly flexible. Further, even after insertion, the valve compresses against the guidewire to establish noticeable friction, or drag, that inhibits the practitioner from reliance on delicate tactile feel of the guidewire's contact with the vessel walls of the patient's vasculature.
It is desired to provide a valve or valve arrangement for a guidewire introducer device that facilitates smooth insertion of a guidewire through the valve or valve arrangement with minimal friction or drag and without snagging or damaging the valve, and permitting both advancement or retraction of the guidewire therethrough during guidewire placement, with minimal friction or drag and without snagging or causing valve damage. The valve must also reseal prior to insertion to maintain the negative pressure created when the bulb is compressed prior to insertion under the skin and then released after insertion.
It is also desired to provide the guidewire introducer device with such a valve for use with, and to permit successful insertion through the valve assembly of, especially small diameter guidewires, such as 0.018 in (0.457 mm), as well as larger diameter guidewires, such as 0.045 in (1.143 mm).
It is further desired to permit enhanced tactile feel transmitted by the guidewire to the practitioner, that is desired by the practitioner during guidewire placement through the vasculature, again especially with very small diameter guidewires.